mkdir <synchronization-folder> && cd <synchronization-folder>
wget https://raw.githubusercontent.com/adidik/git-repos-sync/master/git-repos-sync
chmod +x git-repos-sync

or

mkdir <synchronization-folder> && cd <synchronization-folder>
curl -O https://raw.githubusercontent.com/adidik/git-repos-sync/master/git-repos-sync
chmod +x git-repos-sync

Just run the script with 3 parameters:

• URL of first repository (left).
• URL of second repository (right).
• Branch to sync up.

./git-repos-sync <URL> <URL> <branch>

Both repositories must be accessble on server you execute the script.

On first run script will init Git repository in script's folder and add left and right repositories as remotes. Then first attempt to sync specified branch will be made.

In case if synchronization is not possible because of merge conflict, resolve it manually and just rerun script. It will automatically try to continue syncronization.

In case if sync repo has uncommitted modifications, script will exit with warning.

Script makes next actions to sync up two repos:

1. Fetch specified branch from left repo and right repo.
2. Create sync branch based on right repo branch.
3. Merge left repo branch, if merge conflict, stop for manual resolution.
4. Push sync branch to right repo.
5. Push sync branch to left repo.
6. Remove sync branch.

In case of merge conflict, then:

1. Wait while conflict will be solved manually and commited.
2. Fetch specified branch from left repo and right repo.
3. Merge sync branch with right repo branch, if merge conflict, stop for manual resolution.
4. Merge left repo branch, if merge conflict, stop for manual resolution.
5. Push sync branch to right repo.
6. Push sync branch to left repo.
7. Remove sync branch.

See below different cases.

Initial:

Left repo:  A-B-C <- branch

Sync repo:  A-B-C <-  left/branch, right/branch

Right repo: A-B-C <-branch

Fetch:

Left repo:  A-B-C <- branch

Sync repo:  A-B-C <-  sync-branch, left/branch, right/branch

Right repo: A-B-C <-branch

Merge:

Left repo:  A-B-C <- branch

Sync repo:  A-B-C <-  sync-branch, left/branch, right/branch

Right repo: A-B-C <-branch

Push and remove sync branch:

Left repo:  A-B-C <- branch

Sync repo:  A-B-C <-  left/branch, right/branch

Right repo: A-B-C <-branch

Initial:

Left repo:  A-B-C-D <- branch

Sync repo:  A-B-C <-  left/branch, right/branch

Right repo: A-B-C <-branch

Fetch:

Left repo:  A-B-C-D <- branch

Sync repo:  A-B-C-D <-  left/branch
				^-- sync-branch, right/branch		

Right repo: A-B-C <-branch

Merge:

Left repo:  A-B-C-D <- branch

Sync repo:  A-B-C-D <-  sync-branch, left/branch
				^-- right/branch

Right repo: A-B-C <-branch

Push and remove sync branch:

Left repo:  A-B-C-D <- branch

Sync repo:  A-B-C-D <-  left/branch, right/branch

Right repo: A-B-C-D <-branch

Initial:

Left repo:  A-B-C <- branch

Sync repo:  A-B-C <-  left/branch, right/branch

Right repo: A-B-C-D <-branch

Fetch:

Left repo:  A-B-C <- branch

Sync repo:  A-B-C-D <-  sync-branch, right/branch
				^-- left/branch		

Right repo: A-B-C-D <-branch

Merge:

Left repo:  A-B-C <- branch

Sync repo:  A-B-C-D <- sync-branch, right/branch
				^-- left/branch

Right repo: A-B-C-D <-branch

Push and remove sync branch:

Left repo:  A-B-C-D <- branch

Sync repo:  A-B-C-D <- left/branch, right/branch

Right repo: A-B-C-D <-branch

Initial:

Left repo:  A-B-C-D <- branch

Sync repo:  A-B-C <- left/branch, right/branch

Right repo: A-B-C-E <-branch

Fetch:

Left repo:  A-B-C-D <- branch

Sync repo:  A-B-C-E <- sync-branch, right/branch
				'-D <- left/branch		

Right repo: A-B-C-E <-branch

Merge:

Left repo:  A-B-C-D <- branch

                   ,- right/branch
Sync repo:  A-B-C-E-F <-  sync-branch
				'-D-' <- left/branch	

Right repo: A-B-C-E <-branch

Push and remove sync branch:

Left repo:  A-B-C-E-F <- branch
				'-D-' 

                   
Sync repo:  A-B-C-E-F <- left/branch, right/branch
				'-D-' 

Right repo: A-B-C-E-F <- branch
				'-D-' 

The MIT License (MIT)

Copyright (c) 2015 Aleksey Didik

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.